Technical Field
The present invention relates to a synchronous generator, in particular a multipole synchronous annular generator of a direct-drive wind turbine. The present invention moreover relates to a wind turbine having such a synchronous generator.
Description of the Related Art
In the priority-establishing German application, a search made by the German Patent and Trademark Office identified the following documents: EP 2 752 578 A1, CH 357 797 A and DE 102 44 202 A1.
Wind turbines are generally known. They generate electricity from the wind by means of a generator. Modern direct-drive wind turbines often comprise a multipole synchronous annular generator with a large air gap diameter. The diameter of the air gap is hereby at least four meters and usually is as great as almost five meters. It is absolutely possible for synchronous generators composed of multiple parts to have air gap diameters in the region of ten meters or more.
The efficiency of the synchronous generator has a significant effect on the efficiency of the whole wind turbine when generating power. In order to achieve the highest possible degree of efficiency when generating power, it is therefore important for the stator winding to have an optimum design. This also includes in particular accommodating the highest possible number of bundles of wire in the stator winding.
The greater the thickness of the material of the stator winding, and the greater the induced field of the synchronous generator, the greater the amount of heat generated in the stator winding. It is inevitable that the stator winding and the stator ring of the synchronous generator are heated during operation. It is essential to prevent predetermined temperature limits from being exceeded in order to obviate, for example, impairment of the degree of efficiency or mechanical problems caused by the generation of heat and its transmission to adjoining components.
The generator, in particular the stator ring, accordingly needs to be cooled.
The cooling of the stator ring by means of external cooling means arranged at the circumference of the stator ring is, for example, known from the prior art.
Although this cooling method has been proven to be essentially reliable in practice, there is a requirement to improve the achievable cooling capacity at the synchronous generator of the wind turbine, and in particular at the stator ring.